1. Field of the Invention
The invention relates to a method for measuring and determining a rotation angle of a rotating object in which on a magnetic, optical or optomagnetic storage medium a clock track corresponding to the desired angular resolution is applied, the storage medium is rotated synchronously with the rotating object, in operation a pulse sequence corresponding to the clock track is supplied for further processing to following signal electronics in which the actual rotation angle or the actual angular velocity of the rotating object is available.
2. The Prior Art
As sensors for rotary movements and in conjunction with mechanical measuring means, such as measuring racks or threaded spindles, for linear movements rotation pickups and angle measuring devices are used. Such devices are employed in automation in general mechanical engineering, in robots and handling apparatuses, adjustment and displacement means as well as devices for information technology, antennas, direction devices and also testing and measuring devices of all kinds.
In incremental measurement the output signals of incremental rotation pickups and angle measuring devices are supplied to counting electronics in which the measured value is determined by counting individual "increments". In an incremental rotation pickup the shaft is mounted in a flange with ball bearings set free of play and carries a grating disc of glass on which a radial grating ruling is applied. The opaque lines, which are about twice as wide as the transparent gaps therebetween, consist of chromium which has been evaporated in vacuum to the glass body by the DIADUR method. At a slight distance from the ruling, on the flange a scanning plate is arranged which on small fields carries in each case the same grating ruling or division as the grating disc. However, on the four fields of the scanning plate the lines are arranged respectively , offset by a quarter of a division period. In addition, on the grating disc, as on the scanning disc, a field is applied having a reference mark which with coarser divisions is formed by a single line and with fine divisions by a line group.
All these fields are permeated by a parallel light beam which is generated by a light source and a lens. The light flux is modulated on rotation of the grating disc and impinges on photocells which generate two electrical approximately sinusoidal signals and a reference mark signal. The two sinusoidal signals are electrically 90.degree. out of phase with respect to each other; a signal period of 360.degree. corresponds to a rotation angle through one division period of the radial grating ruling.
With incremental rotation pickups made up in this manner the production is complicated and in addition high angular resolutions and non-linear angle encoding are very difficult to implement; for this reason incremental rotation pickups made in this manner are expensive.
In Michelson interferometers in which rotating retroreflectors are used to generate the path differences, the distance measurement is carried out by means of a laser radiation. The laser radiation passes through the interferometer and from the resultant interference signal, since the wavelength of the laser radiation is known, the path difference can be calculated. A disadvantage in this type of distance or path measurement is that either a reference interferometer for the laser radiation must be coupled to the signal interferometer or the laser radiation must be conducted through the signal interferometer. In the second case a separate region of the beam splitter must be suitable for the laser radiation. As a result, either the region of the signal radiation is restricted or beam splitters, mirrors, lenses and the like larger components must be employed. Furthermore, it is complicated to make a beam splitter which has different optical properties in two geometrically separate regions because the signal radiation usually lies in the infrared whilst the laser is usually an HeNe laser with a wavelength of 632.8 nm. It is further disadvantageous that economical laser tubes as a rule have a low life whilst long-life tubes are expensive.